can you help me to clear the error?
import java.util.*;
class Node{
protected Object data;
protected static ArrayList child;
protected Node next;
public Node(){
next = null;
data = null;
child=new ArrayList();
}
public Node(Object d,Node n){
data = d;
next = n;
n.child=new ArrayList();
}
}
public class Tree{
protected Node head;
public Tree(){
head = null;
}
public boolean isEmpty(){
return head == null;
}
public void insert(Object obj){
if(isEmpty()){
Node.child.add(obj);
head = new Node(obj,head);
}
}
public static void main(String args[])
{
Tree t=new Tree();
Integer j = null;
int i;
System.out.println("starting...");
for(i=0;i<5;i++){
j = new Integer((int)(Math.random() * 100));
t.insert(j);
System.out.println("insert: " + j);
}
System.out.println("Done ;-)");
}
}